1.3Events and Definitions

ACL2 events are special terms which define new functions or logical rules.
Defined names are in scope within their own definition and below; forward
references are not allowed. Use the mutual-recursion event for
mutually recursive functions.

These two forms both define a theorem to be proved and named.
The defthm form defines an enabled function that will be
automatically used in subsequent proof attempts.
The defthmd form defines a disabled function that must be
explicitly mentioned in hints.

Without a :dir option, Dracula adds a ".lisp" extension to the base
name and attempts to load a file relative to the current directory. In the case
above, the program must reside in a directory with a "my-path" subdirectory
containing a book named "my-book.lisp".

Books must be valid Dracula programs; they must start with
(in-package"ACL2"); and they must contain only events, no top-level
expressions.

This variant loads a book from the system directory included with an ACL2
installation. Dracula simulates only a couple of the definitions from these
books, but allows other books to be included for theorem proving purposes. See
ACL2 Books for the list of books supported by Dracula.

The third variant loads one of the books provided with Dracula, called
teachpacks. These books make use of DrScheme features such as interactive
animations and other i/o, and are also reflected in the ACL2 logic. See
Teachpacks for the list of provided teachpacks.

These two forms both define a function.
The defun form defines a logically-enabled function, about which
proof attempts can reason automatically.
The defund form defines a logically-disabled function, about which
proof attempts may only reason if given a hint.